Lock-stitch mechanism for sewing machines



Feb, 26, 1924.;

J. COOPER LOCK STICH MECHANISM FOR SEWING MACHINES Filed Nov. 27. 1920 ATTy.

Patented r set. 1921a LOCK-STITCH MECHANISM FUR SEWING- IVZACEIIN Application filed November 2?, 19:20. Serial No. 426,682.

To all whom it may concern:

Be it known that I, JOSEPH COOPER, a subject of the King of Great Britain and Ireland, of Portland Street Mills, Ashton-underLyne, county of Lancaster, England, have invented new and useful Improvements in Lock-Stitch Mechanism for Sewin Blur chines, of which the following is a specification.

These improvements relate to lock stitch mechanism of sewing machines, of that type of mechanism in which a rotary or oscillating hook rotates around or oscillates about a circular disc or plate bearing a casing for the bobbin or the like of underthread, the periphery of said disc forming a bearing or race for the ring which bears the rotating or oscillating hook. In such machines the needle thread loop engaged by the hook is spread around the bobbin casing, which is open at its front end for the insertion and withdrawal of the bobbin or the like of underthread, and which may have ribsiformed on the rear or closed end of the same to facilitate the passage of the needle thread loop around same. The improvements are particularly applicable to mechanism adapted to receive a bobbin of underthread as it comes from the manufacturer to serve as the underthread, but it will beunderstood from the description which follows that they may be applied to machines in which a wound spool is used as underthread.

The objects of the improvements are to construct a lock stitch mechanism wherein the needle thread loop cannot become entangled on the reversal of the sewing machine; to prevent soiling of the needle thread loop by lubricant; and to prevent the catching of the needle thread loop by the end or flange of the underthread bobbin or the like, should the latter be projecting out of the bobbin casing. In carrying them into effect I make the needle thread gap adjacent to the loop taking hook as narrow as possible consistent with the ethcient and certain engagement of the loop by the said hook, and I cut away the bearing plate or disc at that part where the needle thread loop touches it when being pulled up to form the stitch (after being drawn around the bobbin casing) so that the edge of the cut away portion does not form any part of the bearing for the ring carrying the loop taking hook. Also, I provide on the bearing plate or disc and over the bobbincasing a spreader so arranged that the needle thread loop, while spreading around and over the front and open end of the bobbin casing, will also come upon this spreader and allow the said loop to clear the end of the bobbin.

The accompanying drawings show the improvements as they may be carried into effeet in a lock stitch mechanism of the type described and illustrated in the specification to British Letters Patent No. 134166 granted to the present applicant and others.

In the drawings, which are not to any scale, Figure 1 shows the circular plate or disc around which the needle thread loop taking hook rotates or oscillates, and the bobbin casing fixed therein;

Figure 2 is a side elevation thereof;

Figure 8, is a plan;

Figure 4 shows a view from the open end of the bobbin casing of the mechanism with my improvements and Figure 5 is a side elevation of the complete mechanism as fitted in a sewing machine.

Referring to Figures 1, 2, and 3, A is the plate or disc bearing the bobbin casing, the periphery of which plate or disc forms a bearing for the ring which bears the needle thread loop taking hook. Such plate or disc will be hereinafter referred to as the race plate, and the ring which carries the loop taking hook will be referred to as the hook ring. B is the bobbin casing, adapted to contain and hold upon a central peg or holder C a bobbin of thread as it comes from the manufacturer. (Such a bobbin is shown in position at P in Figures t and 5.) D is a plate of thin metal curved on its upper surface and having curved edges, which plate has formed therewith in course of manufacture the re-turned ends E. F is a tongue adapted to engage with a fixed part on the underside of the sewing machine table to prevent rotation of the race plate A and its contained bobbin casing B. G is an orifice formed in the plate D for the purpose of clearing the needle as the latter descends in the process of forming the needle thread loop for engagement by the hook I-I (shown in Figures l and 5.)

The plate D, which acts as a spreader for the needle thread loop, is preferably fitted to the race plate A at about the angle shown, in applying same to the mechanism fitted with a bobbin casing as illustrated. IVhen the side of the needle thread loop which comes around the lower side of the bobbin casing B passes the open end of the said casing, part of that side of the loop also engages upon the upper surface or the spreader D, with the result that it is pushed a little forwardfrom the race plate and away as shown at J, up to the usual gap M.

The edge of this cut away portion does not therefore form any part of the bearing for the hook ring K, see Figure 4-, and there is therefore no danger of the loop being soiled by lubricant as it passes this part of the race plate A while being pulled up, after passing around the casing, to form the stitch.

As shown in Figures at and 5 the gap formed in thehook ring K to allow of the engagement of the needle thread loop by the hook H is formed of the narrowest possible width. Should therefore the machine be stopped and reversed while the needle thread loop is being engaged by the hook H or while the loop is being spread around the bobbin casing 13, the edge L of the gap which is opposed to the hook H will immediately engage the thr ad of the loop and push it back, thus keeping the loop from loosening and dropping into the mechanism.

It will be noted that the spreader D forming one part of our improvements is made in one piece and solid with the ribs E extending to the rear of the bobbin casing B, and which ribs are already known for the purpose of facilitating the spreading ot' the needle thread loop around the rear of said casing. The race plate A is slotted to allow of the fitting of the spreader D and the ribs or spreaders E at one operation, the formation of the spreader and rlbs as one, and the single operation of fittlng the three,

decreasing the cost of production besides ensuring correct positioning of the Spreaders. The tongue F may also be formed from the material or the spreader D if desired, and be bent to the required shape.

Figure 5, shows in side elevation the mecha nism with our improvements, fixed. to the underside of the sewing machine table. The hook H is shown at about the point where the take up motion of the machine comes into action to pull up the stitch, through the gap in the hook ring K between hook. H and the opposite edge L. The hook ring K may be rotated or oscillated in any convenientman- 1161' from the mechanism of the sewing machine, through a shaft N and spider O on which latter the hook ring K is'secured. The peg or holder C for the bobbin ofunderthread, and the tensioning device for said underthread, may be of the usual or any suitable construction. 7

Claim. V V

In. a lock stitch mechanism for sewing machines, the combinationofa ring having formed therein a hook adapted to engage the needle thread loop and pass it around the bobbin of the underthread, a race plate carrying a bobbin'casing in a position inclined to the vertical, said race'plate forming a bearing for said ring, and having a portion of its periphery cut away to form a recess between it and the ring, and a spreading device comprising aplate secured to said bobbin casing and having its upper suface curved, said spreading, plate being provided with a pair of integral ribs 611- JOSEPH coornn. 

